CVE-2025-21493 is a vulnerability in Oracle MySQL Server affecting versions 8.4.3 and earlier, and 9.1.0 and earlier. The flaw resides in the server's security privileges component, where a high privileged attacker with network access through multiple protocols can exploit the vulnerability to cause the MySQL Server to hang or crash repeatedly, resulting in a complete denial of service (DoS). The vulnerability is difficult to exploit because it requires the attacker to have high privileges on the MySQL Server and network access, but it does not require user interaction. The CVSS 3.1 base score is 4.4, reflecting a medium severity primarily due to its impact on availability (no confidentiality or integrity impact). The vulnerability is categorized under CWE-770, which involves allocation of resources without limits or throttling, leading to resource exhaustion or deadlock conditions. No known exploits have been reported in the wild, and no official patches have been released at the time of publication. The vulnerability affects multiple protocols used by MySQL Server, increasing the attack surface for privileged attackers. Successful exploitation can disrupt database availability, impacting dependent applications and services.

For European organizations, the primary impact of CVE-2025-21493 is the potential for denial of service on MySQL Server instances. This can lead to downtime of critical applications relying on MySQL databases, including web services, enterprise resource planning (ERP) systems, and customer relationship management (CRM) platforms. The disruption can affect business continuity, cause financial losses, and damage reputation. Since the vulnerability requires high privileges, the risk is elevated in environments where internal threat actors or compromised administrative accounts exist. Organizations with extensive MySQL deployments, especially in sectors like finance, telecommunications, and government, may face operational disruptions. The lack of confidentiality or integrity impact reduces the risk of data breaches but does not mitigate the operational risks associated with service unavailability. The absence of known exploits in the wild currently lowers immediate risk but does not preclude future exploitation attempts.

European organizations should implement strict network segmentation and access controls to limit MySQL Server network exposure, ensuring only trusted, authenticated administrators have network access. Monitoring and alerting for unusual MySQL server crashes or hangs should be established to detect potential exploitation attempts early. Administrators should review and minimize the number of users with high privileges on MySQL servers to reduce the attack surface. Employing rate limiting and resource usage monitoring on MySQL services can help detect and prevent resource exhaustion scenarios related to CWE-770. Organizations should prepare for rapid deployment of official patches once Oracle releases them, including testing in staging environments to ensure stability. Additionally, consider implementing failover or high availability configurations for MySQL to mitigate impact from potential DoS events. Regular security audits and privilege reviews are recommended to maintain a secure MySQL environment.